The entertainment industry is involved in a continual struggle to keep movies from being illegally copied. Unfortunately, the same technological advances that have made distributing high quality movies easier have made high quality illegal copies easier to produce. Of particular concern is the copying of high-bandwidth digital video content such as DVDs. Various methods have been employed to protect the content of DVDs from being copied illegally. One such method has been to equip DVD players with Macrovision, or a similar copy protection system. Common copy protection systems allow a media player to detect connections to multiple recording devices, and to scramble or otherwise alter the video data so that quality copies cannot be made. Because of the importance of preventing high quality copies from being made, a more secure form of copy protection, known as Content Scrambling System (CSS), was developed. Using CSS, the content of a DVD is encrypted, allowing the content of the DVD to be read only through the use of an encryption key stored on the DVD and a decryption key stored on the DVD player.
The use of encryption to protect DVDs from being illegally copied has been used much more frequently as DVD use has expanded. Many computers are being sold with built-in DVD-ROM drives and software players. While the content of the video and audio data in the DVD is encrypted, once the DVD player software has decoded the content, the content is decrypted and unsecured. The decoder must re-encrypt the content before submitting them to the video hardware. Video controllers can be made with stored keys that correspond to encryption keys on the decoder, allowing the content received to be decrypted and processed. However, the key cannot be shared amongst multiple decoders. Therefore, a system capable of securely handling data from multiple decoders would be advantageous.